The present invention relates generally to a portable image display, and more particularly to a portable image display that can be added to portable telephones or portable information terminals.
In recent years, image displays, especially head or face mounted image displays designed to allow individuals to enjoy images on large screens or for other purposes have been under intensive developments. With the recent spread of portable telephones or information terminals, there is also a growing demand for viewing images or textual information on portable telephones or information terminals on large screens.
Among head mounted image displays known so far in the art, there is a display system comprising a CRT or other image display device, an image transmission device for transmitting an image on the image display device to an object plane and a toric reflecting surface for projecting the image on the object plane in the air (see U.S. Pat. No. 4,026,641). There is also available a refraction type image display system comprising a relay optical device for forming an image on a liquid crystal display (LCD) or other image display device in the air, and an eyepiece optical device including a decentered concave mirror for guiding the thus formed image to the eyeball of an observer (see JP-A 06-294943).
However, these systems, because of using a large optical system, are found to be unsuitable for use on portable telephones or information terminals.